Portable video oculography system with integral light stimulus system

ABSTRACT

A goggle based light-weight VOG system includes at least one digital camera connected to and powered by a laptop computer through a firewire connection together with an integral visual light stimulus source. The digital camera may digitally center the pupil in both the X and Y directions. A calibration mechanism may be incorporated onto the goggle base. An EOG system may also be incorporated directly into the goggle. The VOG system may track and record 3-D movement of the eye, track pupil dilation, head position and goggle slippage. An animated eye display provides data in a more meaningful fashion. The VOG system is a modular design whereby the same goggle frame or base is used to build a variety of digital camera VOG systems.

RELATED APPLICATIONS

This application is a divisional application of pending U.S. patentapplication Ser. 10/704,529 filed Nov. 7, 2003 entitled Portable VideoOculography System and which published May 12, 2005 as publicationnumber 2005-0099601, which publication is incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to clinical eye tracking systems, and moreparticularly to a self-contained, portable video-oculography gogglesystem with integral light stimulus system.

2. Background Information

Accurate eye position recording and monitoring in three dimensions(3D-yaw, pitch and torsion rotation about line of sight) is asignificant clinical diagnostic tool in the field of vestibulardisorders such as vertigo and other neurological disorders. Anon-invasive technique for recording eye position relative to the headis to use a camera to record eye position relative to the head, known asvideoculography or VOG. VOG systems are used by Vestibular Researchers,Ophthalmologist, Otolaryngologists, Physical Therapists, Neurologists,Audiologists, Balance Clinicians, Neurophysiologists, Physiologists,Neuroscientists, Occupational Therapists, and others. Image processingsoftware is utilized to interpret the images to provide objective dataof eye position. This is described in “A GEOMETRIC BASIS FOR MEASUREMENTOF THREE-DIMENSIONAL EYE POSITION USING IMAGE PROCESSING” Vision Res.Volume 36. No. 3, Moore et al., pp 445-459, 1996, which is incorporatedherein by reference.

The existing VOG systems can be categorized as either earth mounted orhead mounted systems. The oldest method uses earth fixed cameras andattempt to limit movement of the head. The relative movement of the headand the camera would be interpreted as eye movement. These systemsattempt to stabilize or immobilize the head with head holders, headrests, chin rests, or bite bars. Although archaic, this type of systemis still used extensively in some laboratories and many clinicalenvironments. The biggest disadvantage of these systems is the inabilityto remove all head movement. Even the smallest head movements (e.g.resulting from breathing, talking, involuntary postural modification,and from fatigue etc.) cause significant inaccuracy in the measured eyemovement. These systems are particularly unsuitable when inertialstimuli (e.g. a rotational chair) are delivered to a subject in order toproduce vestibular responses, since these stimuli also tend to generatehead movement. This equipment is often heavy and bulky since it must bestrong enough to support and attempt to restrain the head of a subject.

Another classification of earth mounted VOG systems are systems thatattempt to measure eye movement using a space fixed (earth mounted)camera without a head holder mechanism. In general, these systemsattempt to deal with head movement by first tracking the head and thenthe eye within the head. In practice, a subject must actively suppresstheir head movements to within a small range of translations in order tostay within view of the camera. Further, rotations of the head are quitedifficult to detect using image processing and so these systems sufferfrom an inability to distinguish between a change of eye position in thehead or a change of head position during maintained gaze. These systemsmust also use a wide-angle lens in order to digitize an image thatincludes the head movements. Consequently, little picture resolution isavailable for the analysis of the eye position. As a result of theselimitations, these systems are generally only able to measure horizontaland vertical changes in relative eye/head position

Another earth mounted VOG system attempts to measure the eye position byfirst tracking the position of the head and then moving a camera ormirrors to get an image of the eye with higher magnification andresolution. These systems also share many of the disadvantages of theother VOG earth fixed camera systems including the inability toaccurately distinguish between head translation and rotation. Further,the mechanisms used can be complicated expensive noisy and distracting.

A second classification of VOG systems is the head mounted system. Inone type of head mounted VOG system, head mounted cameras are supportedby an adjustable headband often modified from the insert from a miningor welding helmet. The cameras may be mounted above the eyes and aredirected down towards hot mirrors that reflect an infrared image of theeye. Head mounted eye movement recording systems are less prone to theerrors from head movement, because the cameras move with head. Furtherthis method for attaching the cameras to the head is particularlypopular because the headsets can be easily fitted to any subject withoutmodification. The camera mounting position above the eyes also seemsfairly natural because hardware tends to stick up into the air. Thisplacement keeps the centre of gravity closer to the head and reduces theinertial lag on yaw head movements. Despite these advantages, all headmounted video eye movement measurement systems obviously suffer from theneed to wear equipment and be connected, via leads, to the analysishardware. Further, the headband can be painful if it is tightened enoughto effectively suppress slippage of the headset during head movement.

The camera may also be mounted to the side of the headband head mountedVOG systems. The main advantage of mounting cameras to the side ratherthan above the eyes is that the centre of mass of the headset tend to befurther back towards the head and so these headsets don't tends to pitchthe subject's head forward as much as some other arrangements. Thiscamera position also can provide better power supply and data outputaccess (i.e. the electrical and control feeds). The main disadvantage ofthis mounting position is that the headsets tend to become quite wide.These headsets tend to move relative to the head during the yaw headmovements that are common during vestibular testing.

The camera may also be mounted in front of headband in the headband headmounted VOG systems. The main advantage from mounting cameras towardsthe front of the subject is that no hot mirrors are required to reflectan image of the eye into the cameras. This lack of hot mirrorssimplifies the construction and adjustment of the headsets and mayimprove the quality of video images. However, while front mountedcameras might suit light occluded systems where darkness prevents thesubject from seeing them, they don't suit most video headsets that useheadbands because these may not have an open field of view. Apart fromthe obstruction to vision, cameras in front of the subject can providevisual suppression and orientation cues that may affect their eyemovement responses. The headsets with front mounted cameras also tend tohave a centre of gravity that is further away from the head.

In place of the headband, some head mounted VOG systems utilize goggles,similar to those on diving masks, in order to attach cameras to thesubjects face. These headsets benefit from a silicon skirt that conformsto the face and stabilizes the cameras. Goggles also leave the headclear for the use of other devices that may be utilized in variousclinical applications. Another advantage of goggles is that they arewell suited for the construction of light occluding headsets as well asthose with an open field of view, or those that are convertible betweenthe two. The disadvantage of goggles style head mounted VOG systems isthat they can be uncomfortable if the cameras and other hardware is toheavy and ways down on the subjects face.

Some research head mounted VOG systems use video cameras mounted on theheadset with individually molded plastic or fiberglass masks. Thesemasks are particularly stable and good at suppressing relative cameraand head movement. Molded masks also tend to spread the weight of thevideo headset over a large surface area and do not produce the pressurepoints characteristic of some other methods. However, individuallymolded masks can be time-consuming and costly to make and are thereforenot convenient for the clinical testing of large numbers of patients.Hybrid masks that combine a headband and standard molded mask section donot have these disadvantages but do not seem to benefit from theadvantages either.

Another head mounted VOG system utilizes a helmet for camera mounting.The helmet style video headset benefits from a more even distribution ofweight over the top of the head and from the balance provided by moreweight towards the back. Helmet style video headsets are heavier thanmany other systems and so they tend to shift around during vigorous headmovement. They are also quite bulky and prevent the application of headholders.

Another head mounted VOG system utilizes standard glasses construction(i.e. spectacle) for camera mounting. The advantages of spectacle typevideo headsets are that they can be very small and light, and are easilytransportable. The disadvantages of this method include the discomfortfrom heavy equipment resting on the bridge of the nose. With very smallcontact area, spectacles can also be prone to movement relative to thehead in response to inertial forces.

There remains a need for truly portable VOG systems. Further, therecontinues to be a need for accurate meaningful output for the cliniciansin VOG systems without significant discomfort to the patients.

The above discussion concentrates on the deficiencies in the mechanicaldesign of existing VOG systems. In addition to those issues, existingVOG systems are designed as one-of-a kind testing structures. Thisapproach leads to expensive end products. Existing VOG systems alsosuffer from poor camera design, camera power supply issues, datatransfer problems.

Analog cameras in existing VOG systems provide data regarding eyeposition for analysis as is known in the art. During testing the visualimage of the eye(s) is often displayed in real time as a method for theclinician to follow and interpret the data. In other words a real videoimage of the patient is displayed with a graphed display of the data(e.g. a chart of eye vertical and horizontal position change over time).These may also be recorded for later review. The realistic eye image ofthe video does not always easily illustrate movement.

Clinicians have stated that existing VOG systems on the market sufferfrom the following drawbacks: the excessive weight of goggles, theycan't be used with droopy eyelids; difficulty with set-up; torsionalmeasurements not available; lack of the sensor for head positioning;difficulty in viewing eyes; limited in the number of targets presentableto the patient; low sampling rates; software limitations andinflexibility; no ability to focus the camera; and concerns overresolution.

There is a need to address at least some of these problems as well andstill provide a portable, affordable VOG system providing accuratemeaningful output for the clinicians in VOG systems.

SUMMARY OF THE INVENTION

The above stated objects achieved with a portable VOG system accordingto the present invention. A video oculography system according to oneaspect of the invention includes a light-weight head mounted base, suchas goggles, adapted to be attached to a patient's head, at least onecamera attached to the base, a controller coupled to the at least onecamera, the controller providing power and control signals to eachcamera and receiving and storing data signals there from, at least onecamera light source attached to the base, wherein each camera lightsource is associated with one camera attached to the base and isconfigured to illuminate the patient's eye sufficient for the camera toobtain an image of the patient's eye, and at least one visual stimuluslight source attached to the base and distinct from the at least onecamera light source, wherein each visual light source is configured toselectively supply a visual stimulus to a patients eye that is distinctfrom the camera light source.

In one non-limiting embodiment of the invention goggles forming the basemay provide an occluded environment for the patient's eyes. Further, atleast two visual stimulus light sources may be provided for eachpatient's eye in one aspect of the invention. The camera light sourcesand the visual stimulus light sources may be formed in an annular arrayfor at least one of the patient's eyes. The system may further include alaser attached to the base, wherein the laser is visible to theclinician while the patient is wearing the head mounted base. The systemmay provide that the camera light sources have a light wavelength thatis distinct from the light wavelength of the visual stimulus lightsources, such as where the camera light sources are infrared lightsources. In one non-limiting embodiment the camera light sources areformed from a plurality of infrared LEDs and the visual stimulus lightsources are formed from a plurality of visible light LEDs. In a furthernon-limiting embodiment the visual stimulus light source includes afiber optic light that may be centered on the camera.

According to one aspect of the invention the video oculography systemaccording to the invention includes a light-weight head mounted baseadapted to be attached to a patient's head forming an occludedenvironment for at least one of the patient's eyes, at least one cameraattached to the base directed at the patient's eye in an occludedenvironment, a controller coupled to the at least one camera, thecontroller providing power and control signals to each camera andreceiving and storing data signals there from; and an array of lightsources directed at the patients eye in the occluded environment.

According to one aspect of the invention the video oculography systemaccording to the invention includes a modular video oculography systemthat comprises a light-weight head mounted base adapted to be attachedto a patient's head, a plurality of cameras, each selectively attachedto the base, wherein the plurality of cameras may be selectivelyattached to the base to form one of an occluded monocular system and anoccluded binocular system, a controller providing power and controlsignals to each camera attached to the base and receiving and storingdata signals there from, and an annular array of light elementsassociated with each camera.

The portable VOG system according to the present invention is a gogglehead mounted system with at least one digital camera of at least 30 hzgenerally connected to and powered by a computer through a firewireconnection. The computer may be a laptop portable computer (generallyless than about 3 kilograms), whereby the entire system will be lessthan 8 kilograms and preferably less than 5 kilograms, and mostpreferably less than 4 kilograms. The weight of the goggles is criticalin that the lightweight goggles have lower inertia and move lessimproving accuracy of the system. The low inertia goggles of the presentinvention provide a 3d system and weigh less than 500 grams, preferablyless than 300 grams and most preferably less than 200 grams.

The digital camera will allow for digital centering of the patient'spupil at least in one direction through concentrating on the region ofinterest, and preferably in two directions (X and Y). The use of digitalcentering eliminates the need for a mechanical adjustment mechanism(e.g. a slide) in the given direction. Using digital centering for boththe X and Y (yaw and pitch) directions eliminates any gross adjustmentin those directions.

The VOG system according to the present invention incorporates a headfixed calibration mechanism in the form of an integrated laser pointeron the goggle base or camera housing. The calibration mechanism isincorporated directly into the goggle base and powered from the samesource powering the digital cameras. This construction greatlysimplifies and quickens the calibration steps and improves accuracythereof.

The VOG system according to the present invention further incorporatesan EOG (Electro-OculoGraphy) system that can operate independent of orpreferably in conjunction with the VOG system to supplement the acquireddata. The EOG system is incorporated directly into the goggle base andpowered from the same source powering the digital cameras.

The VOG system of the present invention is designed to track and record3-D movement of the eye (generally movement in an X-Y plane and eyerotation or torsion about the line of sight) generally as found in someof the prior art systems, however the present digital based system isdesigned to further track pupil dilation, providing the clinician withfurther critical data for diagnostic testing. The pupil size can becalculated as a byproduct of pupil center calculation using existingpupil center locating technology.

The VOG system of the present invention may further include a headtracking sensor to track and record a patient's head position. The headposition data may be used to supplement other data and possibly toassist in calculating any goggle slip that occurs. Essentially byknowing the goggle mass and inertia values relative to the patient andthe head movement data through a head position sensor an algorithm maybe developed to approximate the goggle position/slippage (e.g.approximating the static and kinetic friction between the skirt of thegoggle and the patient and the force applied by the goggle strap anappropriate algorithm may be developed). Calculated goggle slip can thenbe removed from the eye movement data through appropriate software.

The VOG system of the present invention is designed to provide ananimated eye display with variable, clinician controlled gain to theclinician to provide data in a more meaningful fashion. Specifically,subtle movements are more easily visualized. The animated eye can moreeasily convey position and can include a scaling factor, or gain, tosupplement the illustrated animated eyes. The animation may includevisible indicia, e.g. cross hairs at the pupil center in front view. Inplan view an animated eye may include a line of sight to visiblyillustrate where a given eye is focused on.

The VOG system of the present invention is intended to be a modulardesign in that the same goggle frame or base is used to build monocularfront mounted digital camera VOG systems, binocular front mounteddigital camera VOG systems, monocular side or top mounted digital cameraVOG systems, binocular side or top mounted digital camera VOG systems,etc.

These and other advantages of the present invention will be clarified inthe description of the preferred embodiment together with the attachedfigures were like reference numeral represent like elements throughout.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-3 are perspective views of a goggle for the goggle based VOGaccording to the present invention;

FIG. 4 is a schematic sectional side view of the goggle illustrated inFIGS. 1-3;

FIGS. 5 a and b are schematic sectional side views of alternateadjustment mechanisms for a camera used in the goggle of FIGS. 1-3;

FIG. 6 is a front view of an eye tracking camera assembly for use in theVOG system according to the present invention;

FIG. 7 is a schematic view of a top camera mounted non occludedbinocular VOG system according to the present invention;

FIG. 8 is a schematic view of a top camera mounted monocular goggle fora VOG system according to the present invention; and

FIG. 9 is a view of one type of display available to the clinician inthe VOG system according to the present invention

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1-4 illustrate a goggle headset for a VOG system 10 according tothe present invention. The system 10 is a goggle based system using agoggle frame or base 12 for fitting onto the patient. The base 12 isessentially a frame for swimming or diving goggles such as manufacturedby Technisub S.p.A., and described in U.S. Pat. No. 5,915,541 which isincorporated herein by reference. The base 12 provides a skirt fordistributing the forces around the face and which conforms to the face,and which can be critical for occluded VOG systems. The occluded systemssimply refer to systems where external light is blocked out for at leastone eye. The base 12 is far more universal than an individual faceformed mask.

Each eye portion of the base 12 includes a mounting member 14. Themounting members 14 are used for constructing any of a variety of frontmounted VOG systems in accordance with the present invention. One member14 may be left open to provide a field of view of at least 30 degreeshorizontal and 30 degrees vertical. Alternatively one member 14 may becovered with a cap 15 to provide an occluded monocular system. Anotherembodiment could provide one or two caps 15 each with an optical frenzellens, wherein the clinician can view the patient's eye through frenzellens. In the VOG system shown in FIGS. 1-4 one member 14 receives adigital camera unit 16. Both members 14 could receive a digital cameraunit 16 forming an occluded binocular front mounted VOG system accordingto the present invention.

The digital camera unit 16 includes a digital camera operating at leastat 30 hz (30 frames per second), although 120 hz-200 hz cameras and evenhigher are available. Another aspect of the present invention is theconcept of utilizing the same camera 16 and increasing the operatingcycles by trading off the total resolution. As a representative example,if the pupil location were simulated with ten, five or even points (i.e.a very low resolution image of the eye) than the speed with the samecamera can be drastically increased. Such limited resolution would beimpractical for most diagnostic applications, but may be suitable for asports training application (e.g. baseball batters or golf players).Suitable cameras for the unit 16 are sold under the name iBot camera,StealthFire camera, Firefly II, and Scorpion camera, as a representativesample. Some of these cameras are sold through Point Grey and can befound at http:/www.ptgrey.com/. These cameras typically operate on aregulated 3.3V DC and have a resolution of at least 640×480 althoughhigher resolutions cameras such as 1024×640 are also currentlyavailable. A 480×320 resolution image (or less) is available and may besufficient particularly where one desires a higher transmission rate.

As shown in greater detail in FIGS. 4 and 5 a and b, the camera units 16include an outside mounted Z axis adjustment mechanism 18. Theadjustment mechanism 18 allows for the focus to be adjusted for thecamera unit 16 while the goggle base 12 is on the patient (e.g. fromoutside of the goggle base 12) without allowing light to enter. Theadjustment mechanism 18 is effectively a slide mounting for the cameralens with an adjusting screw for the displacement of the slide in FIG. 5a. Alternatively the mechanism 18 may be a stepper motor, such as in acomputer hard drive, as shown in FIG. 5 b.

Regarding the centering of the camera in the camera unit 16 onto thepupil, the use of high resolution digital cameras allows this to beaccomplished digitally. Specifically when the pupil location isidentified, such as by using the algorithm described in the “A GEOMETRICBASIS FOR MEASUREMENT OF THREE-DIMENSIONAL EYE POSITION USING IMAGEPROCESSING” article discussed above, the software will crop the image tothe region of interest. In other words, the system will ignore the data(after the centering) outside of the relevant portion of the digitalimage (i.e. the region of interest that may be a 460×335 pixel image)centered on the pupil. In this manner the software will avoid the needfor mechanical centering devices, thereby decreasing weight andincreasing system efficiency. Further some cameras may be able to onlyselect a given region of interest in which the data of the unusedportions need not be transmitted, thereby either increasing the speed ofthe transmission or increasing the resolution of the region of interestwhereby the region of interest will be a 640×480 (or 1024×640 or 480×320or less as desired) pixel image of the region of interest. Theelimination of mechanical centering devices with one of the optionsabove is referred to as digital centering within the meaning of thisapplication. The high resolution digital cameras of the VOG system 10allows the system to track and record 3-D movement of the eye (generallymovement in an X-Y plane and rotational movement) and to further trackpupil dilation, providing the clinician with further critical data fordiagnostic testing.

The camera unit 16 also shows a location for a laser 20 which can act asa calibration system for the goggles while on the patient's head. Thelaser 20 will point away from the camera base or goggle base 12 and willbe utilized to calibrate the system 10 such as on a wall a specificdistance away. The laser 20 can also be used to monitor and control headmovement. For example, the clinician may instruct the patient tomaintain the visible laser image of the laser 20 on a specific point ormove this image along a desired path, while the clinician can watch forvariation of the laser image position from the desired location ordesired path. Generally, the cap 15 will be removed and the patientasked to focus his eye on the laser image (e.g. a cross hair, or otherimage) on a surface a known distance away. The laser 20 is fixedrelative to the head and thereby automatically eliminates head movementin this calibration step. In an occluded system the patient may not seethe image of the laser 20, but the clinician can still monitor movement,and the patient need not see the laser image to move his headhorizontally, vertically or maintain no movement of his head. Theintegrated laser 20 is a significant tool for the clinician.

The camera unit 16 may further include a pair of infrared LEDs 22 and apair of visible light LED's 24 facing the patient. The infrared LEDs 22allow the camera to obtain images in an occluded environment and thevisible LEDs 24 allow visual stimulus to be supplied to the patient inan occluded system. The LEDs 22 and 24 can be changed in number,position, color as desired by the clinician, and can be controlled bythe operator. In other words the system 10 can be easily designed toaccommodate any lighting arrangement with LED's as the cliniciansindicate is desirable. As an alternative, a fiber optic light can be runin front of the camera lens, to the center of the camera lens anddirected at the patient whereby the patients focus on the light willalso be centered on the camera. A single fiber optic strand issufficiently thin to avoid interference with the camera image.

A key aspect to forming a portable VOG system according to the presentinvention is the data, the power and the control coupling for the cameraunit 16. The VOG system 10 utilizes an IEEE 1394 cable, also called afirewire cable 28, for each camera unit 16. The firewire carries twotwisted pair of signal wires used for data transmission and a twistedpair of power cables used for power supply. Through the use of digitalcameras, low power LED elements 22 and 24 and laser 20, a 5V powersupply will be sufficient. Such a power supply can be obtained from astandard laptop computer such as computer 30 shown in FIG. 7. Thedigital camera uses a conventional voltage regulator to step down theinput voltage to 3.3 V DC. A typical firewire uses a 6-pin connectionwhich is found on most Macintosh® Laptops, IBM® or compatible desktopsand Macintosh® desktops allowing direct connection thereto. Some laptopsdo not have a 6 pin connection and only have a 4 pin communication linkonly port. A specialized adaptor can be made using a standard fire-wireadaptor (connects the four communication lines) together with a set ofleads to a USB port for power. Other modifications to accommodate thisarrangement may be made (e.g. replace the lead on the camera, or use anadapter, such that it can plug into the iLINK port on a SONY® VAIO whichwill free up the PCMCIA and USB ports for other uses).

The system 10 provides a completely portable system 10 since thecomputer may be a laptop portable computer 30. A conventional laptopcomputer 30 weighs generally less than about 3 kilograms, and thegoggles will generally weigh less than 1 kilogram (and preferably lessthan 300 grams and most preferably 200 grams) whereby the entire systemwill be much less than 8 kilograms and generally less than 5 kilograms(with current laptops the system may be about 4 kilograms). The computer10 may also be replaced with a smaller device such as a subnotebook (notshown), which is used merely for data acquisition and control of thecomponents (rather than analyzing and displaying the data). With the useof a smaller device the weight of the system drops even further to about2 kilograms or less. This system would allow tests to be performedessentially anywhere and the data later transferred to a separatecomputer (even a desktop) for analysis and display. A portable systemwould be those less than about 10 kilograms, since heavier than thatthey will become cumbersome and unwieldy for the clinician. The system10 is of such light weight that the system can be carried by a patient,such as on a rotational chair.

As discussed above the digital camera of the unit 16 will allow fordigital centering of the patient's pupil at least in one direction. Theuse of digital centering eliminates the need for a mechanical adjustmentmechanism (e.g. a slide) in the given direction. Using digital centeringfor both the X and Y directions eliminates any gross adjustment in thosedirections.

The VOG system according to the present invention further incorporatesan EOG system that can operate independent of or preferably inconjunction with the VOG system to supplement the acquired data. The EOGsystem is incorporated directly into the goggle base and powered fromthe same source powering the digital cameras. Specifically the goggleframe 12, and the skirt thereof in particular, provide easy mountinglocations for the sensors needed for conventional EOG system. Thesensors can provide eye location when a patients eyes are closed, whichof course the video system cannot. The firewire 28 allows for the dataof the integrated EOG system to be sent to the computer 30. This datacan be used to correct the eye position data of the VOG system andsupplement such data when the patient's eyes are closed. An integratedEOG/VOG system will thereby provide greater accuracy in the data resultsand provide further testing options to a clinician in a single device.For example, one conventional diagnostic test is to examine eye positionwith eye closure, and the EOG/VOG system allows this test to be easilyaccomplished with other VOG tests. The sensors can be used to convey anyphysiologic data to the clinician, including but not limited to EOGdata. In addition to or in place of the EOG related data the clinicianmay desire the sensors to convey patient temperature, blood flow data,blood pressure data, patient perspiration data, patient heart rate data,goggle position or slippage data, head position data (discussed above),light sensor (occluded systems) or any physiologic data that may bedesired.

The VOG system 10 of may further include a head tracking sensor (notshown) attached to the base 12 to track and record a patient's headposition. Precise position sensors are known in the art such as aninertial measurement unit from Inertial Sciences, Inc. The head positiondata may be used to supplement other data and possibly to assist incalculating any goggle slip that occurs, wherein knowing the goggle massand inertia values relative to the patient and the head movement datathrough a head position sensor an algorithm may be developed toapproximate the goggle position/slippage. Essentially the algorithm mayapproximate the static and kinetic friction between the skirt of thegoggle base 12 and the patient and the force applied by the goggle strapand use the head position data to calculate the acceleration of thepatients head and thereby approximate the goggle slippage. Calculatedgoggle slip can then be removed from the eye movement data throughappropriate software. Another head tracking method is through use of aseparate camera for recording and tracking such movement. Thisadditional system requires a separate imaging processing for the headmovement.

The VOG system 10 provides an animated eye display such as shown in FIG.9 to the clinician to provide data in a more meaningful fashion. Thedetails of animating an eye from given data can be found at thefollowing website: http://user.cs.tu-berlin.de/˜fidodido/StdArbeit/stdarbeit.html which shows eye animation for dataplayback and is incorporated herein by reference. The animated eyes 40can more easily convey position and can include an adjustable scalingfactor, or gain 42, to supplement the illustrated animated eyes. Thegain is for X, Y and rotational or torsional movement (with rotationbeing the most difficult to accurately measure). The controllable gain42 may be separated into the specific components if desired. Theanimation may include visible indicia, such as cross hairs 44, at thepupil center in front view to assist in viewing movement, in particularrotational movement. Additionally a visible line of sight can beprovided in a top view. The digital image and analysis thereof for pupilcenter provide all the real time data needed to construct and move theanimated eyes 40. The eyes 40 may also be displayed with graphical data46.

The VOG system 10 of the present invention is intended to be a modulardesign. There are other high priced convertible systems such as anoccluded/open face/monocular/binocular as can be found at websitehttp://www.smi.de/3d/index.htm. However the system 10 of the presentinvention is modular in that the same goggle frame 12 or base is used tobuild occluded monocular front mounted digital camera VOG system 10 asshown in FIGS. 1-4, or binocular front mounted digital camera VOGsystems, or a monocular top mounted digital camera VOG system 10 asshown in FIG. 8 (in which unit 16 is replaced with a side mounted unit16′ and a hot mirror 50 for reflecting the image into the camera), orbinocular top mounted digital camera VOG system 10 as shown in FIG. 7(with units 16′, hot mirrors 50 and center mounted calibration laser20′), or frenzel goggles with caps 15 having lenses therein, or avariety of other systems through mixing of these components and addingother modular components. As shown in FIGS. 7 and 8 the same mountingmember 14′ can be used for top mounted cameras 16′ and for side mountedcameras wherein the mounting position of the camera and the hot mirrorswould be switched. The key feature is that a wide variety of systems canbe built on a single platform, the goggle frame 12. The clinician canbuild numerous systems through selective combinations of mounts andcameras.

Various modifications of the present invention may be made withoutdeparting from the spirit and scope thereof. For example, the system mayinclude a digitized objective view of the lid position to provide anobjective analysis for ptosis. The described embodiment is not intendedto be restrictive of the present invention. The scope of the presentinvention is intended to be defined by the appended claims andequivalents thereto.

1. A video oculography system comprising: a light-weight head mountedbase adapted to be attached to a patient's head; at least one cameraattached to the base, configured to obtain video images of the patient'seye; a controller coupled to the at least one camera receiving andstoring data signals there from; at least one camera light sourceattached to the base, wherein each camera light source is associatedwith one camera attached to the base and is configured to illuminate thepatient's eye sufficient for the camera to obtain an image of thepatient's eye; and at least one visual stimulus light source attached tothe base and distinct from the at least one camera light source, whereineach visual light source is configured to selectively supply a visualstimulus to the patient's eye simultaneously with the camera obtainingvideo images of the patient's eye, wherein the at least one visualstimulus light is distinct from the camera light source.
 2. The systemof claim 1 wherein the light weight head mounted base is a pair ofgoggles.
 3. The system of claim 2 wherein the goggles provide anoccluded environment for the patient's eyes.
 4. The system of claim 2wherein at least two visual stimulus light sources are provided for eachpatient's eye.
 5. The system of claim 2 wherein the camera light sourcesand the visual stimulus light sources are formed in an annular array forat least one of the patient's eyes.
 6. The system of claim 1 furtherincluding a laser attached to the base, wherein the laser is visible tothe clinician while the patient is wearing the head mounted base.
 7. Thesystem of claim 1 wherein the camera light sources have a lightwavelength that is distinct from the light wavelength of the visualstimulus light sources.
 8. The system of claim 7 wherein the cameralight sources are infrared light sources.
 9. The system of claim 1wherein the camera light sources are formed from a plurality of infraredLEDs and the visual stimulus light sources are formed from a pluralityof visible light LEDs.
 10. The system of claim 1 each visual stimuluslight source includes a fiber optic light.
 11. The system of claim 10wherein fiber optic light is centered on the camera.